Method and apparatus for correcting gage of strip during rolling



March 19, 1963 w. 1.. ROBERTS 3,081,651

METHOD AND APPARATUS FO CORRECTING GAGE OF STRIP DURING ROLLING 2 Sheets-Sheet 1 Filed April 28, 1960 20A 61 L200 1 i 22A DIFFERENT/AL $6511 2:- 32 DIFFERENT/AL AMPLIFIER 20 321 22 AMPLIFIER POWER sou/res //V VEN TOR W/LL/AM L. ROBERTS March 19, 1963 w. L. ROBERTS 3,031,651

METHOD AND APPARATUS FOR CORRECTING GAGE OF STRIP DURING ROLLING Filed April 28, 1960 2 Sheets-Sheet 2 56* Q I PIEQB 4 56R DIFFERENT/AL V74 72/? AMPLIFIER E=="| a0 L gap #37 l/VVE/VTOR W/LL/AM L. ROBERTS Aflorney ite rates 3,'8l,ti5l Patented Mar. 19, 1963 3,031,651 METHOD AND APPARATUS FOR (IORRECTING GAGE F STRIP DUREQG ROLLING William L. Roberts, Murrysville, Pa, assignor to United States Steel Corporation, a corporation of New Jersey Filed Apr. 28, 1960, Ser. No. 25,337 7 Claims. (Cl. 80-35) This invention relates to a method and apparatus for rolling strip and more particularly to the rolling of steel strip in a tandem cold rolling mill. In the rolling of strip it is essential to maintain the thickness of the strip at a uniform value within tolerance limits. Variations in the gage of the strip, particularly across its width, may result in a commercially unacceptable product, difiiculty in keeping the material along the pass line of the mill and difficulty in coiling the rolled strip. In the rolling mill art it is well known that the amount of reduction in thickness of the strip is dependent upon the gap between the work rolls, the physical characteristics of the strip and the tension on the strip. Greater reduction in thickness may be obtained by decreasing the gap between rolls and/ or increasing the tension of the strip. When the roll gap is set to a certain value the adjustment is made so that the gap will be constant across the width of the pass. This alone is not enough to assure uniform thickness of the strip because the work rolls may flex or wear out unevenly or the temperature across the strip may vary so as to cause a different amount of reduction across the strip width. Therefore, even though the workpiece is symmetrical across its width, it may be rolled with a greater reduction on one side than on the other with the result that a product of varying gage is produced.

It is therefore an object of my invention to provlde a method of rolling strip wherein the tension across the Width of the strip is controlled to obtain uniform strip a e. g another object of my invention is to provide apparatus for automatically controlling tension across the width of the strip in accordance with gage variations in the strip.

These and other objects will be more apparent after referring to the following specification and attached drawings, in which:

FIGURE 1 is a schematic utilizing my invention;

FIGURE 2 is a schematic diagram of a preferred embodiment of my invention;

FIGURE 3 is a schematic diagram of a second embodiment of my invention;

FIGURE 4 is a cross sectional view of a strip having one type of contour often encountered;

FIGURE 5 is a schematic view showing the position of the guide rolls while correcting for the strip condition shown in FIGURE 4;

FIGURE 6 is a cross sectional view of a strip having a second type of contour often encountered; and

FIGURE 7 is a schematic view showing the posit on of the guide rolls while correcting for the strip condition shown in FIGURE 6.

Referring more particularly to FIGURE 1 of the drawings, reference numeral 2 indicates the work rolls of one stand of a tandem cold rolling mill through which strip S passes to work rolls 4 of a second stand. It will be understood that the usual back-up rolls will be provided in each roll stand. Located between the sets of work rolls 2 and 4 are tension or guide rolls 5 which are carried by a structure to be described hereinafter. The rolls 5 are tilted in such a manner that the tension on the near edge S of the strip S is greater than that on the far edge S A bracket 1%, which is preferably rigidly mounted on the frame of the mill so that it will not move diagram of a cold strip mill relative to the normal pass line of the strip, is provided at the exit side of the work rolls 4. Attached to the bracket 10 is an arm 12 on which are mounted three thickness gages 14, 16 and 18. The thickness gages 14, 16 and 18 may be of any conventional type, such as flyingmicrometer or X-ray, but I prefer to use X-ray gages. The thickness gage 14 is located adjacent one edge of the strip S, the thickness gage 16 near the center of the strip S, and the thickness gage 18 adjacent the other edge of the strip S. The gages 14, 16 and 18 are preferably slidably mounted on the arm 12 so that they may be moved horizontally to accommodate various widths of strip. The thickness gages 14, 16 and 18 each produce an output voltage which is proportional to the thickness of the strip passing beneath the respective gag-e. The negative terminals of the thickness gages 14, 16 and 18 are connected to input terminal 20B of a differential amplifier 20 and to input terminal 22B of a differential amplifier 22. The positive terminal of the thickness gage 14 is connected to the input terminal 20A of the differential amplifier 20 and the positive terminal of the thickness gage 18 is connected to the input terminal 22A of the differential amplifier 22. The positive terminal of the thickness gage 16 is connected to the input terminals 20C and 22C of the differential amplifiers 20 and 22, respectively. The differential amplifier 20 has four output terminals 20D, 20D, 2GB and 29E. The differential amplifier 22 has four output terminals 221]), 22D, 22B and 22E. Because the amplifiers 2t and 22 are identical, the operation of only one will be described in detail. When the voltage applied across the terminals 20A and 20B of the differential amplifier 26 is substantially equal to the voltage across the terminals 20B and 20C, no signal is present at the output terminals 20D, 20D, 20B and 20E. When the voltage across the terminals 20A and 20B exceeds the voltage across the terminals 20B and 29C a voltage is produced across the output terminals 20D and 29D, but not across the output terminals 20E and 20E. When the voltage across the terminals 291% and 20C exceeds the voltage across the terminals 20A and 203 a voltage is produced across the output terminals 2tlE and 2913', but not across the output terminals 20D and 26D. A relay coil 24 having a normally open contact 24C is connected across the terminals 20D and 2tiD; relay coil 26 having a normally open contact 26C is connected across the terminals 20E and 20B; relay coil 28 having an normally open contact 28C is connected across the terminals 22D and 22D; and relay coil 30 having a normally open contact 360 is connected across the terminals 22E and 22B. Positive terminal 32? of a direct current power source 32 is connected through the contact 240 to one armature terminal 34A of a motor 34. The other armature terminal 34A of the motor 34 is connected to ground which in this embodiment is the steel frame of the strip mill. The field winding of the motor 34 which is not shown is supplied with power in a conventional manner. The negative terminal 32N of the power source 32 is connected to ground. Also connected to ground is positive terminal 361 of a direct current power source 36 which is identical to the power source 32. The negative terminal 36N of the power source 36 is connected to the armature terminal 34A of motor 34- through normally closed limit switch 38 and contact 26C. The limit switch 38 is a conventional element and its function will be explained in detail hereinafter. The positive terminal 32F of the power source 32 is also connected through contact 28C to one terminal 40A of the armature of motor 40 which is identical to motor 34. The other armature terminal 40A of the motor 42' is connected to ground. The negative terminal 36N of the power source 36 is connected to the armature terminal 40A of the motor 40 through normally closed a limit switch 42 and contact 30C. The limit switch 42 is identical to limit switch 33. The motor 34 has a threaded shaft 348 which is received in a tapped hole in member 44 so as to raise or lower member 44 as the shaft 348 rotates. Thus the rotation of shaft 345 will cause the member 44 to move up or down, depending on the direction of rotation of the shaft 348. When member 44 is moved above the normal pass line it will open limit switch 38. The motor 49 has a threaded shaft 408 which is received in a tapped hole in member 46. When member 46 is moved below the normal pass line it will open limit switch 42. The tension rolls are supported in a housing 48 which is here shown as a circular member but may be of any shape which will accommodate the tension rolls 5. The rolls 5 rotate in bearings 54) mounted in housing 48. Provision may also be made to adjust the gap between the rolls 5 in any conventional manner to provide for strip of various thicknesses. The housing 48 has two flanges 52 and 53 having elongated slots 54 and 55 therein. Pins 44F and 461 are secured to members 44 and 46, respectively, in any suitable manner and are received in slots 54 and 55, respectively.

The operation of my device is as follows:

Assuming that the shape of the rolled strip is as shown in FIGURE 4, the thickness gage 14 which measures the strip thickness X will produce an output voltage greater than the voltage prod-need by the thickness gage 16, which measures the strip thickness Y. Because of this difference in voltage, the signal across the terminals 20A and 203 will exceed that across the terminals 20B and 20C so that relay coil 24 will be energized causing its contact 24C to close. This closure causes the shaft 345 of the motor 34 to rotate so as to move the member 44 downwardly. The output voltage of thickness gage 18, which measures the strip thickness Z will exceed that of thickness gage 16 with the result that the signal across the terminals 22A and 228 will exceed the signal across the terminals 22B and 22C so that coil 28 will be energized to close its contact 280 and cause the shaft 408 of motor 40 to rotate so as to move the member 46 upwardly. When the members 44 and 46 have moved as explained above, the guide rolls 5 will be in the position shown in FIGURE 5 with the result that the tension on the strip at its edges will exceed the tension at its center. This increased tension will cause a greater reduction in gage at the edges and the nonuniformity will be corrected. With the condition corrected, the voltage output of thickness gages 14 and 18 will no longer exceed the output of gage 16 and the coils 24 and 28 will be deenergized, thereby causing the shafts 34S and 408 to stop rotating. If overcorrection occurs the voltage output of gage 16 will exceed the outputs of each of the gages 14 and 18. Because of the differences between the voltages from gages 14 and 16 the differential amplifier 20 will energize the coil 26 and close its contact 26C. This causes motor 34 to rotate the shaft 348 so as to cause the member 44 to move upwardly. This upward movement will cease either when the outputs of the gages 14 and 16 are equal or when the member 44 opens switch 38. Because of the differences between the voltages from gages 16 and 18 the amplifier 22 will energize the coil 30 and close its contact 30C. This causes the motor 40 to rotate the shaft 468 in a direction to move the member 46 downwardly, which movement will cease either when the outputs of the gages 16 and 18 are equal or when the member 46 opens the switch 42. The above steps will be repeated as gage variations are detected by the thickness gages 14, 16 and 18.

Assuming that the shape of the rolled strip is as shown in FIGURE 6, the output voltage of gage 16, which measures thickness Y, will exceed that of gage 14, which measures thickness X and the amplifier 20 will energize coil 26 so as to close its contact 26C. This will connect power to the motor 34 so as to rotate shaft 348 in the direction to move the arm 44 upwardly until it opens the switch 38. The output of gage 18, which measures thickness Z, will exceed the output of the gage 16 so as to cause the differential amplifier 22 to energize the coil 28 so as to close its contact 28C. The motor 40 will be energized so as to rotate the shaft 408 in the .direction to move the arm 46 upwardly. Thus the tension rolls 5 are positioned as shown in FIGURE 7. When the rolls 5 are so positioned the tension on the right side of the strip will exceed that on the left side with the result that greater reduction will occur at the right side of the strip. When the nonuniformity is corrected the output of gage 18 will no longer exceed the output of gage 16 and the contact 28C will open, stopping the rotation of shaft 405. r If overcorrection occurs the output of gage 16 will exceed that of gage 18 and the contact 30C will close. The motor 40 will then cause the shaft 498 to rotate so as to move the member 46 downwardly. This downward movement will continue until the outputs of the gages 16 and 18 are equal or until the limit switch 42 is opened by the member 46. If the strip is thicker at its left edge than at its right edge the member 46 will remain stationary and the member 44 will move downwardly so as to increase the tension on the left side of the strip.

In the embodiment of my invention shown in FIGURE 3 the work rolls 4 are shown mounted in a roll housing '56 which has a right vertical member 56R and a left vertical member 56L. Mounted on the vertical member 56R between the center lines of the work rolls 4 is a strain gage 58R electrically connected in a bridge circuit 60R. The bridge 60R includes fixed resistors 62R, 64R and 66R, a variable resistor 68R and a battery 70R. The junction of the strain gage 58R and the fixed resistor 62R is grounded. Mounted on the left vertical member 56L is a strain gage 58L located in the same manner as the strain gage 58R with respect to the center line of the work rolls 4. Associated with the strain gage SSL is a bridge circuit 60L made up of fixed resistors 62L, 64L and 66L, a variable resistor 68L, and a battery 70L. The junction of the strain gage 58L and the fixed resistor 62L is grounded. Although I have shown strain gages associated with bridges in this embodiment as a means for measuring the thickness of the strip S, I have found that any suitable thickness gage, such as fiying-micrometer-type gage or X-ray gage, may be substituted for the gage shown. The moving contact of the variable resistor 68R is connected by a wire 72R to an input terminal 74A of a differential amplifier 74 and the moving contact of the variable resistor 68L is connected by a wire 72L to the other input terminal 74B of the amplifier 74. The differential amplifier 74 is of a conventional type and has four output terminals 74C, 74C, 74D and 74D. The amplifier 74 is so arranged that, when the voltage (regardless of polarity) with respect to ground at the input terminal 74A exceeds that the input terminal 74B, a voltage is produced across the output terminals 74C and 74C, but not across the output terminals 74D and 74D and when the voltage with respect to ground at the input terminal 74B exceeds that at the input terminal 74A a voltage is produced across the output terminals 74D and 74D but not across the output terminals 74C and 740'. A relay coil 76 having two normally open contacts 76C and 76C]; is connected across the output terminals 74C and 74C of amplifier 74. A relay coil 78 having normally open contacts 78C and 78C1 is connected across the output terminals 74D and 74D of amplifier 74. The positive terminal 8GP of a direct current power source 80 is connected through the contact 78C and contact 820 of a limit switch 82 to an armature terminal 84A of a motor 84. The limit switch 82 has normally closed contacts 82C and 82C1 and normally open contacts 82C2 and 82C3. The positive terminal 80F is also connected through contacts 78C and 82C2 to armature terminal 86B of a motor 86. The negative terminal 80N of the power source 80 is connected through contacts 78C1 and 82C1 to the armature terminal 84B of motor 84 and is also connected through contacts 78C1 and 82C3 to armature terminal 86A of motor 86. The positive terminal 80P of power source 80 is connected through contact 76C and through contact 88C of a limit switch 88 to the armature terminal 86A of motor 86. The limit switch 88 has normally closed contacts 88C and 88C1 and normally open contacts 88C2 and 88C3-. The positive terminal 801 of power source 80 is also connected through contacts 76C and 88C2 to the armature terminal 84B of motor 84. The negative terminal 80N of power source 80 is connected through contacts 76C1 and 88C1 to the armature terminal 86B of the motor 86 and is also connected through the contacts 76C1 and 88C3 to the armature terminal 84A of motor 84. The motors 84 and 86 are conventional with standard field winding connections which are not shown. The motor 84 has a threaded shaft 848 which is received in a threaded hole in member 90 so that the member 90 will move upwardly or downwardly depending upon the direction of rotation of the shaft 848. In like manner the motor 86 has a threaded shaft 868 arranged to rotate in a threaded hole in member 92 which is substantially identical to member 90. The members 90 and 92 include pins 90? and 92P, respectively, which are arranged to fit loosely into elongated slots 93 and 94, respectively, in a housing 95. The tension roll 5- is rotatably supported in bearings 100- mounted in housing 95. The members 90 and 92 operate the limit switches 82 and 88, respectively, when the top of the tension roll 5 is lowered to the normal pass line of the strip.

The operation of this embodiment of my invention is as follows:

Assuming that the shape of the strip passing through the rolls 4 is as shown in FIGURE 6, the output of bridge 60R will exceed that of bridge 60L with the result that the differential amplifier 74- will energize the relay coil 76. If the member 92 is above its lowest position the contacts 88C and 88C1 will be closed and therefore the closure of contacts 76C and 76C1 will energize the motor 86 and cause the shaft 868 to rotate so as to move the member 92 downwardly. When the member 92 has moved downwardly to the point at which the top of tension roll 5 is on the same level as the normal pass line of the strip the limit switch 88 will be operated so as to open its contacts 88C and 88C1 and close its contacts 88C? and 88C3. This will provide power to motor 84 through contacts 88C2 and 88C?! and the shaft 848 will rotate so as to move the member 90 upwardly. This upward movement will increase the tension along the right edge of the strip so as to increase gage reduction at this point. At this time the tension roll 5 will assume a position similar to that of the lower roll of FIGURE 7. When the gage distortion has been corrected the outputs of the bridges 60R and 60L will become equal and the coil 76 will be deenergized causing the shaft 84S to stop rotating. If overcorrection occurs; that is, if the distortion in thickness becomes opposite to that shown in FIG- URE 6, the output of the bridge 60L will exceed that of the bridge 60R and the differential amplifier 74 will energize the relay coil 78 closing its contacts 78C and 78C1. This connects power to motor 84 through contacts 82C and 82C1. The shaft 845 will then rotate so as to move the member 90 downwardly until it operates the limit switch 82. Actuation of switch 82 opens its contacts 820 and 82C]. and closes its contacts 82C2 and 82C3 with the result that the motor 86 begins to rotate in the direction to raise the member 92 and increase the tension near the left side of the strip. This, of course, causes greater reduction near the left side of the strip. When the distortion is corrected the output of the bridge 60L will become equal to that of the bridge 60R, the coil 78 will be deenergized, the contacts 78C and 78C1 will open, and the shaft 868 will stop rotating. The procedure 6 described above will continue as variations in thickness are detected by the strain gages 58R and 58L.

While two embodiments of my invention have been shown and described, it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim:

1. The method of rolling strip comprising passing the strip under tension between a first pair of reducing rolls and a second pair of reducing rolls in sequence, measuring the thickness of the strip emerging from the second pair of rolls at a plurality of transverse zones as related to the total width of the strip, and varying the tension transversely of the strip in each zone in accordance with the thickness Of the strip in the respective zone.

2. The method of rolling strip comprising passing the strip under tension between a first pair of reducing rolls and a second pair of reducing rolls in sequence, measuring the thickness of the strip emerging from the second pair of rolls at a plurality of transverse positions, and

increasing the tension on that transverse portion of the strip having the maximum gage without increasing the tension on the transverse portion of the strip having the minimum gage.

3. Apparatus for rolling strip comprising a first pair of reducing rolls through which the strip passes, a second pair of reducing rolls through which the strip passes from the first pair of rolls, means for tensioning the strip in its travel from said first pair of rolls to said second pair of rolls, gage means for measuring the thickness of the strip emerging from the second pair of rolls at a plurality of transverse positions, and means responsive to said gage means for varying said tension transversely of the strip in accordance with var-ration in transverse thickness of the strip.

4. Apparatus for rolling strip comprising a first pair of reducing rolis through which the strip passes, a second pair of reducing nolls through which the strip passes from the first pair of rolls, a tension roll between said. first and second pairs of rolls over which the strip passes, means for moving the ends of said tension roll with respect to one another in a plane substantially normal to the surface of said strip, gage means for measuring the thickness of the strip emerging from the second pair of rolls at a plurality of transverse positions, and means responsive to said gage means for actuating said tension roll moving means to vary the position of said tension roll in accordance with the variation in thickness transverse of said Strip.

5. Apparatus for rolling strip comprising a first pair of reducing rolls through which the strip passes, a second pair of reducing rolls through which the strip passes from the first pair of rolls, a tension roll between said first and second pairs of rolls over which the strip passes, means for moving the ends of said tension roll with respect to one another in a plane substantially normal to the surface of said strip, a gage for measuring the thickness of one edge of the strip emerging from the second pair of rolls, a gage for measuring the thickness of the other edge of the strip emerging from the second pair of rolls, and means responsive to said gages for actuating said tension roll moving means to move that end of the tension roll in line with the thick edge of said strip away from the normal strip pass line.

6. Apparatus for rolling strip comprising a first pair of reducing rolls through which the strip passes, a second pair of reducing rolls through which the strip passes from the first pair of rolls, a pair of tension rolls between said first and second pairs of rolls between which the strip passes, means for moving one end of each of said tension rolls with respect to its other end in a plane substantially normal to the surface of said strip, gage means for measuring the thickness of the strip emerging from the second pair of rolls at a plurality of transverse positions, and means responsive to said gage means for varying the tension transversely of the strip in accordance with variation in thickness transverse of the strip.

7. Apparatus for rolling strip comprising a first pair of reducing rolls through which the strip passes, a second pair of reducing rolls through which the strip passes from the first pair of rolls, a pair of tension rolls between said first and second pairs of rolls between which the :strip passes, means for moving one end of each of said tension rolls with respect to its other end in a plane substantially normal to the surface of said strip, said last named means including a first motor associated with the first edge of the strip and a second motor associated with the second edge of the strip, a gage for measuring the thickness of the said first edge of the strip emerging from, the second pair of rolls, a gage for measuring the thickness of the said second edge of the strip emerging from the second pair of rolls, means responsive to said gages for actuating said first motor when said first gage reading is greater than said second gage reading to move its end of the roll away from the normal strip pass line, and means responsive to said gages for actuating said second motor when said second gage reading is greater than said first gage reading to move its end of the roll away from the normal strip pass line.

1 References Cited in the file of this patent UNITED STATES PATENTS 2,100,653 Umansky Nov. 30, 1937 2,268,217 Lessmann Dec. 30, 1941 2,300,990 Stoltz Nov. 3, 1942 2,332,272 Shayne Oct. 19, 1943 2,792,730 @0220 May 21, 1957 3,006,225 Mamas Oct. 31, 1961 

1. THE METHOD OF ROLLING STRIP COMPRISING PASSING THE STRIP UNDER TENSION BETWEEN A FIRST PAIR OF REDUCING ROLLS AND A SECOND PAIR OF REDUCING ROLLS IN SEQUENCE, MEASURING THE THICKNESS OF THE STRIP EMERGING FROM THE SECOND PAIR OF ROLLS AT A PLURALITY OF TRANSVERSE ZONES AS RELATED TO THE TOTAL WIDTH OF THE STRIP, AND VARYING THE TENSION TRANSVERSELY OF THE STRIP IN EACH ZONE IN ACCORDANCE WITH THE THICKNESS OF THE STRIP IN THE RESPECTIVE ZONE. 